#include <stdio.h>
#include <stdlib.h>

int main (int argc, char const* argv[])
{
    int i;
	float arr[12], sum;

	for (i=0; i<12; i++) {
		scanf("%f", &arr[i]);
	}

    sum = 0.0;
	for (i=0; i<12; i++) {
		sum += arr[i];	
	}

    printf("$%.2f\n", sum / 12);

    return 0;
}
